In the previous post, we have discussed on the 1st criterion for predicting the products of electrolysis for Aqueous Solutions, that is to determine the Position of Metals In The Reactivity Series.
Today, we are going to look at the 2nd criterion, that is:
Effect of Concentration of Solution on Effective Discharge
- It applies only to ANIONS
- Only for Concentrated Solutions
- An increase in the concentration of an anion tends to promote its discharge
Example:
Consider Electrolysis of concentrated NaCl solution using carbon electrodes.
2 types of anions are attracted to the anode: Cl- and OH- ions
According to the reactivity series, OH- ions should be discharged preferentially (as we have seen in the previous post on diluted aqueous solutions). However, Cl- ions are far more numerous than OH- ions and so are discharged instead.
Try out this question to see if you understand this concept.
Question:
What would you observe when a concentrated solution of HCl is electrolyzed using Platinum electrode? Explain your observations and write down the equations involved.
PS: Remember to leave down your comments and suggested answers in the “Leave Your Reply” section below.
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During the electrolysis of concentrated HCl solution, bubbles would form on each platinum electrode, whereby at the anode, chlorine gas will be generated. The reaction at the anode would be
2Cl^- + 2e^- ==> Cl2
Hydrogen would be discharged at the cathode according to the following equation,
2H^+ ==> H2 + 2e^-
Reply
sean Reply:
October 13th, 2008 at 1:57 am
Hi Bella,
Well Done! Your answer is correct.
The way your explained the answer is detailed enough too!
Keep Up The Good Work!
Sean Chua
Master Trainer @ SimpleChemConcepts.com
Author for UP YOUR CHEMISTRY GRADES NOW! book
Reply
Is there any difference for inert electrode and other electrodes?
The equation of reaction at the electrode seems to be the same for other electrodes?
Reply
sean Reply:
November 1st, 2009 at 12:25 am
Yes there is a difference when you use Reactive Electrodes VS Inert Electrodes.
Look at some examples to prove it.
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